Along with the rapid distribution of information-related equipment and communication equipment such as personal computers, video cameras, and mobile telephones in recent years, the development of batteries that are utilized as electric power sources thereof has been considered important. Furthermore, the development of high output power and high capacity batteries for electric vehicles or hybrid vehicles is in progress in the field of automobile industry and the like as well. Currently, among various batteries, lithium batteries are attracting attention because of its high energy densities.
In regard to the lithium batteries that are currently available in the market, since liquid electrolytes including flammable organic solvents are used, installation of safety devices that suppress temperature increase at the time of short circuits, and devices for preventing short circuits are needed. Meanwhile, since lithium batteries that have been produced into all solid state batteries by converting the liquid electrolyte to a solid electrolyte layer do not use flammable organic solvents in the batteries, it is contemplated that simplification of safety devices can be promoted, and the lithium batteries are excellent in view of the production cost and productivity.
Patent Literature 1 discloses a secondary battery in which a cathode and an anode are disposed through an electrolyte. The secondary battery is configured in a state in which an active material layer is not formed on an anode current collector during assembly, and an alkali metal and the like precipitate onto the anode current collector during charging. An object of this technology is to improve a battery capacity.
In addition, Patent Literature 2 discloses a method of manufacturing a lithium ion secondary battery. In the method, a concavo-convex shape is formed on surfaces of a cathode active material layer and an anode active material layer, respectively, a solid electrolyte layer is disposed between the cathode active material layer and the anode active material layer, and then a heating treatment is performed. In addition, as a pitch of the concavo-convex shape, a pitch of 20 nm to 1 μm is described. In this technology, the concavo-convex shape is formed, and thus a contact area between the solid electrolyte layer, the cathode active material layer, and the anode active material layer is increased.
In addition, Patent Literature 3 discloses a lithium ion secondary battery using a solid electrolyte layer in which concavity and convexity are formed on a surface thereof. In the lithium ion secondary battery, a cathode and/or an anode have a surface shape conforming to the concavity and convexity. In addition, as a shape of the concavity and convexity, a linear shape having a depth of approximately 180 μm is disclosed. In this technology, the concavo-convex shape is formed, and thus a contact area between the solid electrolyte layer and the electrodes is increased.
In addition, Patent Literature 4 discloses a lithium secondary battery which includes a cathode, an anode, and a nonaqueous electrolyte, and in which Rz on a lithium metal precipitation surface of an anode current collector is 10 μm or less. Patent Literature 4 discloses a configuration in which Rz is made to be small, and thus a current distribution on an anode current collector surface can be uniform, and generation of dendrite can be suppressed.